1. Field of the Invention
The present invention relates to a robot for a production machine which is used as a product removal apparatus for removing products from a production machine such as an injection molding machine, or as an insert-part-loading apparatus for loading an insert part into a mold or the like.
2. Description of the Relevant Art
There has been known a product removal apparatus (robot for a production machine) which removes a product ejected from a mold of an injection molding machine and transports the product to a product container disposed adjacent to the injection molding machine.
A conventionally-used product removal apparatus is a traverse-type product removal apparatus which is designed to move linearly a chuck capable of holding and releasing a product along X, Y, and Z directions. However, such a traverse-type product removal apparatus involves a drawback in that since the apparatus must have a size corresponding to the stroke of movement of the chuck along each direction, the apparatus is comparatively large overall, and an installation space corresponding to the stroke of movement is required.
In order to solve the above-described drawback, Japanese Utility Model Publication Nos. 4 (1992)-45861, 5 (1993)-40989, and others propose an improved product removal apparatus in which an articulated robot having a plurality of linked arm portions is used in order to reduce movement area to thereby reduce the size and installation space.
Meanwhile, a mold clamp apparatus of an injection molding machine includes four tie bars, which slidably support a movable platen to which is attached a movable die. Therefore, a molded product must be removed through a space between the tie bars without causing interference with the tie bars. Accordingly, the chuck of a product removal apparatus must be moved linearly at lest along the vertical direction, and the chuck must be maintained in a constant posture (orientation). In the case of the above-described articulated robot, since fundamental motions are produced by means of rotation of respective joint portions, when the chuck is to be moved linearly, two arm portions must be moved in a combined manner through simultaneous control of rotational angles of the two arm portions.
However, when a chuck is secured to a distal end of an articulated arm, the orientation of the chuck changes depending on the rotational angles of the arm portions. Therefore, the conventional product removal apparatus of the articulated robot type which has been provided in injection molding machines requires an additional drive mechanism for correcting the orientation of the chuck. This results in an increase in the number of parts, an increase in difficulty in designing a control system, and an increase in cost stemming from an increased degree of complexity of hardware and software. Further, the overall size and weight of the part removal apparatus increase.
An object of the present invention is to provide a robot for a production machine which is advantageously disposed in an injection molding machine and which can stably and smoothly remove a molded product through a space between tie bars without causing interference with the tie bars, even when the molded product is large.
Another object of the present invention is to provide a robot for a production machine which can simplify hardware and software to thereby reduce the overall cost of the apparatus, as well as the size and weight of the apparatus.
These and other objects are accomplished by a robot for a production machine comprising a support base; a first vertical arm portion having a first base portion supported on the support base; a first rotational drive section for rotating the first arm portion; a second vertical arm portion having a second base portion supported on a distal portion of the first arm portion, wherein said first and second vertical arms extend vertically in a direction parallel with a height of said support base and are rotatable in a direction normal to a horizontal direction of said support base; a second rotational drive section for rotating the second arm portion; a chuck supported on a distal portion of the second arm portion, wherein a first base-side pulley is disposed at the first base portion; a first distal-side pulley is disposed at the distal portion of the first arm portion; a second base-side pulley is disposed at the base portion of the second arm portion; and a second distal-side pulley is disposed at the distal portion of the second arm portion, wherein the first base-side pulley is fixed to the support base, the chuck is fixed to the second distal-side pulley, the first distal-side pulley and the second base-side pulley are connected to each other via a connection shaft, the first base-side pulley and the first distal-side pulley are connected to each other via a first rotation transmission section, and the second base-side pulley and the second distal-side pulley are connected to each other via a second rotation transmission section.
Thus, an articulated robot arm having first and second arm portions is constructed. The first arm portion is swung by means of the first rotational drive section, and the second arm portion is swung by means of the second rotational drive section. The chuck is fixed to the second distal-side pulley, and the second distal-side pulley is operatively connected to the first base-side pulley via a rotation transmission mechanism including the second rotation transmission section, the second base-side pulley, the first distal-side pulley, and the first rotation transmission section, and the first base-side pulley is fixed to the support base. That is, the chuck is operatively connected to the fixed first base-side pulley via a rotation transmission system independent of drive systems of the first and second arm portions. Therefore, when the diameter of the first base-side pulley is rendered the same as that of the first distal-side pulley and the diameter of the second base-side pulley is rendered the same as that of the second distal-side pulley, rotation of the first arm portion relative to the first base-side pulley is transmitted to the chuck as is, and rotation of the second arm portion relative to the first arm portion is transmitted to the chuck as is. Since the first base-side pulley is fixed and does not rotate, the chuck has a constant orientation regardless of variations in the rotational angles of the first and second arm portions.